Method of rolling on a pilger mill

ABSTRACT

A method of pilger rolling is disclosed which employs a pilger mill which comprises spaced die rolls mounted for continuous rotation about fixed axes. The feeding and rolling are effected intermittently step by step. A step of feeding of the successive portion of a blank into the gap between rolls and the next step of rolling this portion are effected during one revolution of the rolls. The directions of blank movement are opposite in feeding and rolling. A device is provided between the drive motor and the rolls to convert the uniform rotation of the drive motor into a periodically varying rotation of rolls. Thus the rotary speed of the rolls is varied periodically within each revolution so that the rate of speed during feeding is lower than that when the feeding is arrested and the successive portion of blank is rolled. Several different forms of device are provided, such as an elliptical gear train, multilink and slide block mechanisms.

United States Patent [54] METHOD OF ROLLING ON A PILGER MILL 11 Claims, 10 Drawing Figs.

52 use: 72/249, 72/208 [51] 1mm: ..B21b35/00 so FieldofSearch 72/249,

Primary ExaminerMilton S. Mehr Attorney-Waters, Roditi, Schwartz and Nissen ABSTRACT: A method of pilger rolling is disclosed which employs a pilger mill which comprises spaced die rolls mounted for continuous rotation about fixed axes. The feeding and rolling are effected intermittently step by step. A step of feeding of the successive portion of a blank into the gap between rolls and the next step of rolling this portion are effected during one revolution of the rolls. The directions of blank movement are opposite in feeding and rolling. A device is provided between the drive motor and the rolls to convert the uniform rotation of the drive motor into a periodically varying rotation of rolls. Thus the rotary speed of the rolls is varied periodically within each revolution so that the rate of speed during feeding is lower than that when the feeding is arrested and the successive portion of blank is rolled. Several difi'erent forms of device are provided, such as an elliptical gear train, multilink and slide block mechanisms.

Patented May, 25, 1971 6 Sheets-Sheet 1 Patented May 25, 1971 6 Sheets-Sheet 2 O 0 h I i u I I Patented May 25, 1971 6 Sheets-Sheet 5 Patented May 25, 1971 6 Sheets-Sheet 4 Patented May 25, 1971 6 Sheets-Sheet 5 I [III [II/I F/E'Ji Fig.7

Patented May, 25, 1971 6 Sheets-Sheet 6 METHOD OF ROLLING ON A PILGER MILL The present invention relates to methods of rolling metals, mainly to methods of rolling tubes and to devices for effecting same, and more particularly to methods of rolling on a pilger mill and to a roll drive for effecting same.

For producing tubes, pilger mills are used that feature a periodically intermittent rolling process. In these mills during each revolution of the stationary mounted work rolls, one cycle of deforming the blank and one cycle of feeding it into the roll gap take place in succession.

Circular grooves on the surface of the rolls of the pilger mill are divided into two sections, one of which, the working section, serves for deforming the blank and is shaped in accordance with the adopted mode of rolling, while the second section, an idle one, is used for feeding the blank and is shaped so that the gap between the rolls will ensure a free passage of the blank being fed.

For feeding the blank a so-called feeding apparatus is used, which, during the time when the gap between the rolls is formed by the idle sections thereof, effects the travel of the blank over a distance corresponding to the length of the working strokeI The value of said time interval is directly related with the number of revolutions of the uniformly rotating rolls, and this number, in turn, determines the mill efficiency. Hence, the efficiency of the pilger mill is in a direct relationship with the high speed of the feeding apparatus.

However, considerable difficulties are encountered when attempts are made to increase the high speed of the feeding apparatus and these difficulties actually limit the possibility of further increasing the number of revolutions of the rolls and, therefore, hinder an increase in the efficiency of the known pilger mills.

It is an object of the present invention to provide such a method of rolling on a pilger mill and, accordingly, such appropriate means for effecting same, which will make it possible to increase the number of revolutions of the rolls and thus to increase the efficiency of the mill, without recourse to increasing the high speed of the feeding apparatus.

This object is attained in the present invention dueto the employment of such a method of rolling on a pilger mill according to which the blank is periodically deformed by the rolls continuously rotating in the same direction and having a variable contour of the roll pass, the blank being fed into the roll gap between each two deformation periods, the idle section of the circular groove of each roll being used for the purpose. According to the invention, the rolls are caused to rotate at a speed periodically varying within each revolution, such that during the feed of the blank the rotation speed of the rolls is smaller than during the working period. A slower rotation of the rolls during the period of the blank feed makes this period longer and thus enables increase in the number of revolutions of the rolls and, accordingly, the efficiency of the pilger mill without any necessity in increasing the high speed of the feeding apparatus.

The invention can be employed in a pilger mill in which the roll drive comprises conventional means for transmitting the torque from the motor to each roll of the mill. According to the present invention, the drive connection between the motor and the work rolls incorporated a device which converts the uniform rotation of the drive into a rotation of the work rolls whose speed periodically varies within each revolution.

The device for converting the rotation, according to the invention, may be made as a transmission with noncircular, for example, elliptical gears. For a stepless variation of the nonuniformity of rotation of the rolls, it is expedient for the device for converting the rotation to be made as a multilink parallelcrank mechanism, in which the driving and the driven members are made rotatable, and their hearing supports are mounted so that their axles are shiftable with respect to each other and adapted to be fixed in a required position.

Such an embodiment of the roll drive of the pilger mill makes it possible to set the optimum value of the degree of nonuniformity of rotation of the rolls in accordance with the characteristics of the available feeding apparatus and with the technological requirements of the rolling process.

In the multilink parallel-crank mechanism employed in compliance with the present invention, one of the rotatable members may be made as a link movably connected with another rotatable member made as a crank through a third member made as a slider.

To make the device for converting the rotation compact and simple in design, it is constructed as a combination of two four-link parallel-crank mechanisms, in which the driving rotary member of the first mechanism and the driven rotary member of the second mechanism are fixedly connected to the shaft of the motor and to the input shaft of the pinion stand of the mill, respectively, while the rigidly interconnected driven rotary member of the first mechanism and the driving rotary member of the second mechanism are mounted in a common support adapted for transverse travel with respect to the common axis of rotation of the interconnected members and for fixing in a required position.

It is also possible to make the multilink parallel-crank mechanism according to the invention in such a manner, that the driven rotary member in the form of a crank is rigidly fixed on the shaft of the motor and, through an intermediate member made as a slider, is movably connected with the driven rotary member which is made as a link and rigidly fixed on the input shaft of the pinion stand, the latter being mounted with the possibility of transverse movement with respect to the axes of rotation of the above-mentioned members and adapted to be fixed in a required position.

The use of the present invention ensures an increase in the efficiency of the pilger mill by at least 30 per cent.

Given hereinbelow is-a description of exemplary embodiments of the present invention to be taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagrammatic elevational view, partly in section, of the roll drive of a pilger mill with a device for converting the rotation;

FIG. 2 is a section taken along line 11-1! of FIG. 1 (on an enlarged scale);

FIG. 3 is a perspective view of a multilink parallel-crank mechanism, according to the invention for converting the uniform rotation;

FIG. 4 is an elevational view partly in section of the multilink parallel-crank mechanism, according to the invention;

FIG. 5 is a section taken along line V-V of FIG. 4 (on an enlarged scale);

FIG. 6 is an elevational view partly in section of another embodiment according to the invention;

FIG. 7 is a section taken along line VII-VII of FIG. 6 (on an enlarged scale);

FIG. 8 is a perspective view of another embodiment of a device for converting the rotation;

FIG. 9 is an elevational view partly in section of a device for converting the rotation, wherein the link of the multilink parallel-crank mechanism is fixed on the shaft of the movable pinion stand, according to the invention; and

FIG. 10 is a section taken along line X-X of FIG. 9 (on an enlarged scale).

The roll drive of the pilger mill (FIG. 1) comprises a motor 1, a device 2 for converting uniform rotation into nonuniform rotation, couplings 3 connecting motor 1 and device 2, a pinion stand 4 which distributes the torque between two rolls 5 of the mill, and spindles 6 which connect each of the rolls with the pinion stand.

The device for converting unifonn rotation into a nonuniform one (FIG. 2) comprises noncircular gears 7, 8 and is intended for a drive operation when the degree of the nonuniformity of rotation of the rolls is not varied. The gears 7, 8 are elliptical and in mesh within a casing. One of the gears, 8, is fitted onto a shaft 9 connected with the shaft of the motor 1 by means of the coupling 3, and the second gear, 7, is fitted onto a shaft 10 connected with the input shaft of the pinion stand 4.

If the degree of the nonuniformity of rotation is to be smoothly controlled, the device is expediently made as a multilink parallel-crank mechanism as shown in FIGS. 3, 4 and 5.

In accordance with this embodiment, a hollow input shaft 11 of the device, connected through the coupling 3 with the motor, is mounted in pedestal bearings 12 (FIG. 4) fixed on a frame 13.

The input shaft 11 (FIG. is made integral with a crank 14, preferably as a single casting. The crank 14 is connected by means of a hinge 15 with one end of a connecting rod 16, whose other end is connected by means of a hinge 17 with a rim 18 (FIGS. 4 and 5) that functions as cranks l8 and 18" (FIG. 3). By means of balance bearing rollers 19 the rim I8 is tumably mounted in a sledge 20 which travels along guides 21 (transverse in relation to the longitudinal axis of the drive) on the frame 13 (FIG. 4). The axis of rotation of the rim 18 is parallel to the axis of rotation of the crank 14, and the distance between these axes is adjusted by shifting the sledge 20 along the guides 21 on the frame 13. In the place diametrally opposite the hinge 17, the rim 18 is connected by means of a hinge 22 with one of the ends of a connecting rod 23, whose other end is connected by means of a hinge 24 with a crank 25, rigidly fitted onto an output shaft 26 mounted in bearings inside the input shaft 1 1.

For the crank 25 (FIG. 5) to protrude from inside the shaft 11, the external surface of the latter is provided with a port whose size is sufficient for the relative travel of the crank 25 and the shaft 11 in the course of operation of the device.

The output shaft 26 (FIG. 4) is connected with the pinion stand 4 by means of a coupling 27. If the degree of the nonuniformity of rotation is to be varied within an especially wide range, it is expedient that in the above-described multilink mechanism one of each two rotary members interconnected by a connecting connecting rod be made as a crank, other as a link; and the interconnecting rod be converted into a slider that slides in a groove of the link and is hinged to the crank. A preferred embodiment of such a device 2 as a crank-and-link version is shown in FIGS. 6 and 7, and its connections are shown in FIG. 8.

According to said embodiment, a hollow input shaft 28 of the device (FIG. 6) connected by means of the coupling 3 with the motor, is mounted in pedestal bearings 29 fixed on a frame 30. The input shaft is made integral with a crank 31, preferably as a single casting.

The crank 31 (FIG. 7) is connected by means of a hinge 32 with a slider 33 which is free to slide in a radial groove 34 made in a rim 35 (FIG. 7) which functions as links 35 and 35" (FIG. 8). The rim 35 by means of balancing bearing rollers 36 is tumably mounted in a sledge 37 travelling along guides 38 (transverse with respect to the longitudinal axis of the drive) on the frame 30. The axis of rotation of the rim 35 is parallel to the axis of rotation of the crank 31, and the distance between said axes is adjusted by shifting the sledge 37 along the guides 38 on the frame (FIG. 6). In the place of the rim diametrally opposite the radial groove 34 (FIG. 6 and 7) a radial groove 39 is provided in which a slider 40 is free to slide, said slider being connected with a crank 41 by means of a hinge 42. The crank 41 is fixedly fitted onto an output shaft 43 mounted in bearings 44 (FIG. 6) inside the input shaft. The output shaft 43 is connected by means of the coupling 27 with the pinion stand 4.

Simplification of the design of the device for converting the rotation which is pennissible in certain cases, may be attained by fixing a crank 45 directly on the shaft of the motor (FIGS. 9 and 10) and by fixing a link 47 associated with the crank 45 through a slider 46 directly on the shaft of the pinion stand 4. Then the pinion stand 4 is movably mounted on transverse guides 48 and can, through the intermediary of an appropriate device, not shown in the drawing, be fixed in a position that ensures the required distance between the parallel axes of rotation of the crank and the link.

The principle of operation of the device 2 made as a transmission with elliptical gears is based on a periodic variation during one revolution of the instantaneous gear ratio of said transmission. (The average ratio per revolution is equal to unity, that is, during one complete revolution of the driving gear the driven gear also performs one revolution). The required ratio between the maximum and minimum speeds of rotation within one revolution (that is, the degree of nonuniformity) is ensured by the choice of the appropriate shape of the noncircular gears. The greater the ellipticity of the gear, that is, the greater the ratio between the semiaxes of the ellipse, the greater the degree of nonuniformity of rotation.

In the device made as a multilink parallel-crank mechanism, a complete revolution of one rotary member involves a complete revolution of another rotary member connected with the first-mentioned member through a nonrotary intermediate member (a connecting rod or a slider).

Thus, the average gear ratio is equal to unity. However, the instantaneous gear ratios continuously vary, periodically increasing and decreasing within each revolution.

The degree of nonuniformity of rotation attained by such mechanism depends on the mutual arrangement of the rotary members and, hence, can be controlled by adjusting the distance between their axes of rotation.

The distance between the centers is adjusted by appropriately shifting the sledges 20 and 37, whereupon they are fixed in position.

The present invention is not limited to the exemplary embodiments described hereinabove and various modifications are possible such as fall within the spirit and scope of the appended claims.

We claim:

1. A method of pilger rolling involving the intermittent feeding and rolling of successive portions of a blank into a gap formedbetween die rolls, comprising rotating the die rolls continuously, and imparting to the rolls a rotary speed which periodically varies within each revolution so that the rate of speed during the feeding of the blank is lower than that when feeding is arrested and a portion of the blank is rolled.

2. A pilger mill for rolling successive intermittently advanced banks, comprising rotatable die rolls having gaps for rolling successive portions of a blank, means for rotating the rolls continuously about fixed axes to operate on successive portions of a blank, and means for periodically varying the speed of rotation of the rolls within each revolution thereof.

3. A pilger mill as claimed in claim 2 in which said means for rotating the rolls continuously comprises a drive motor having uniform rotation, said means for periodically varying the speed of rotation of the rolls including a transmission between the drive motor and rolls having conversion means such that the uniform rotation of the drive motor is converted into a periodically varied rotation of the rolls.

4. A pilger mill as claimed in claim 3 in which said conversion means comprises noncircular gears.

5. A pilger mill as claimed in claim 3 in which said conversion means comprises a multilink parallel-crank mechanism including rotary driving and driven members having bearing supports mounted to enable the axes of rotation to be moved relative to each other.

6. A pilger mill as claimed in claim 5 including fixing means for fixing the bearing supports in position.

7. A pilger mill as claimed in claim 5 wherein at least one rotary member serves as a link movably associated with another rotary member made as a crank through a third member.

8. A pilger mill as claimed in claim 5 in which the conversion means comprises two four-link parallel-crank mechanisms and the driving rotary member of the first mechanism and the driven rotary member of the second mechanism are rigidly connected, respectively, with the shaft of the motor and with the input shaft of a pinion stand of the mill, the driven member of the first mechanism and the driving member of the second mechanism being rigidly interconnected and mounted for common transverse movement with respect to the common axis of rotation of the members mounted therein.

nected to the input shaft of a pinion stand which is movable in a transverse direction relative to the axes of rotation of the members.

11. A pilger mill as claimed in claim 10 including fixing means for fixing the transverse position of the pinion stand. 

1. A method oF pilger rolling involving the intermittent feeding and rolling of successive portions of a blank into a gap formed between die rolls, comprising rotating the die rolls continuously, and imparting to the rolls a rotary speed which periodically varies within each revolution so that the rate of speed during the feeding of the blank is lower than that when feeding is arrested and a portion of the blank is rolled.
 2. A pilger mill for rolling successive intermittently advanced banks, comprising rotatable die rolls having gaps for rolling successive portions of a blank, means for rotating the rolls continuously about fixed axes to operate on successive portions of a blank, and means for periodically varying the speed of rotation of the rolls within each revolution thereof.
 3. A pilger mill as claimed in claim 2 in which said means for rotating the rolls continuously comprises a drive motor having uniform rotation, said means for periodically varying the speed of rotation of the rolls including a transmission between the drive motor and rolls having conversion means such that the uniform rotation of the drive motor is converted into a periodically varied rotation of the rolls.
 4. A pilger mill as claimed in claim 3 in which said conversion means comprises noncircular gears.
 5. A pilger mill as claimed in claim 3 in which said conversion means comprises a multilink parallel-crank mechanism including rotary driving and driven members having bearing supports mounted to enable the axes of rotation to be moved relative to each other.
 6. A pilger mill as claimed in claim 5 including fixing means for fixing the bearing supports in position.
 7. A pilger mill as claimed in claim 5 wherein at least one rotary member serves as a link movably associated with another rotary member made as a crank through a third member.
 8. A pilger mill as claimed in claim 5 in which the conversion means comprises two four-link parallel-crank mechanisms and the driving rotary member of the first mechanism and the driven rotary member of the second mechanism are rigidly connected, respectively, with the shaft of the motor and with the input shaft of a pinion stand of the mill, the driven member of the first mechanism and the driving member of the second mechanism being rigidly interconnected and mounted for common transverse movement with respect to the common axis of rotation of the members mounted therein.
 9. A pilger mill as claimed in claim 8 including fixing means for fixing the transverse position of the driven member and driving member.
 10. A pilger mill as claimed in claim 5 wherein the driving member of the multilink parallel-crank mechanism is rigidly connected to the shaft of the motor and the driven rotary member associated with the driving member is rigidly connected to the input shaft of a pinion stand which is movable in a transverse direction relative to the axes of rotation of the members.
 11. A pilger mill as claimed in claim 10 including fixing means for fixing the transverse position of the pinion stand. 